Nowadays methods for suppressing the use of a mobile communications network are used chiefly in penal facilities (JVA), in order to prohibit the inmates of the penal facility from an uncontrolled communication with the outside world by means of a mobile phone. This goal is achieved, in particular, through the use of jammers, which suppress a communications connection between the mobile phone and the mobile communications network. The drawback has turned out to be that jammers of this type produce an interference field that can be delimited in terms of space only with difficulty. Thus, in particular, the residents who live in the vicinity of the penal facility are restricted in their possibilities for using the mobile communications network.